In general, the injection molding machine uses oil pressure as a driving source. The use of oil pressure involves many problems, and particularly, the instability to the operation of the machine resulting from a change in viscosity of hydraulic oil greatly influences the injection molding of resins. In addition, expensive hydraulic devices, for example, a hydraulic pump, various kinds of hydraulic control valves, a hydraulic cylinder, a hydraulic motor, a heat exchanger, etc. are required, and moreover, management of temperatures and contamination of hydraulic oil, and exchange of hydraulic oil resulting from deterioration are also required.
As one of means for solving the problem raised when oil pressure is used as a driving source as described above, it is considered that the machine is operated by the electric motor. In fact, it has been partly suggested that the electric motor is used in the injection molding machine. However, this is not that the injection molding machine is totally operated by the electric motor but the clamping mechanism is used as means for rotating a screw of the injection mechanism and merely used jointly with oil pressure.
In the injection molding machine, the difficulty involved in the accomplishment of the entire process by the same electric motor lies in the responsiveness of a normal electric motor. Unlike the cutting work of articles, the injection molding includes a speed control region and a force control region in one molding cycle. Accordingly, the injection molding machine cannot be operated by one electric motor unless the electric motor is actuated in response to said regions.
In accordance with this invention, a servo-motor used for machine tools or the like is used to drive the injection molding machine to continuously carry out the processes from the clamping of a mold to the injection of molten resin, thus solving various problems caused by oil pressure in prior arts. Furthermore, it is an object of the present invention to provide a machine wherein a required number of clutches and brakes are used to convert the rotation of the servo-motor into a force, thereby generating a clamping force, an injection force and the like equivalent to those cases where oil pressure is used, and making it possible to achieve injection molding without use of oil pressure.